In a conventional respirator containing active carbon filtering elements, as the molded respirator containing sorbent particles disclosed in U.S. Pat. No. 6,234,171 B1, the sorbent particles 11 (active carbon is used in most cases) are attached to the fabric 1. Due to the limited quantity of sorbent particles 11 attached to the unit area of the fabric 1, the unit area can be easily saturated and lose its efficiency, resulting in failure to satisfy the user's need to wear the respirator 2 for an extended period of time. Therefore, some manufacturers have provided such consumers (users) with a respirator 2 containing a filter can 20, such as models shown in FIGS. 2 and 3, using a plurality of filtering materials 21 contained in the filter can 20 of the respirator 2, in the hope of effectively filtering off organic toxic gases, inhibiting the regeneration of germs, eliminating bad odors, and extending the service life of effective filtering performance.
Such conventional models of respirator 2 containing a filter can 20, however, has a breathing area limited to the size of the outflow diameter 201 of the filter can 20, resulting in an air flow constriction as illustrated in FIG. 3. As a result, in extended use, the user often feels difficulty in breathing effort. Furthermore, due to gravitational force, the filtering particles 21 contained inside the filter can 20 would naturally develop a condition of differential pressure, with upper layer of filtering particles 211 compressing on lower layers of filtering particles 212,213. As a result, air filtered in and passing the filter can could easily form channels 22 through the upper layer of filtering particles 211 where the pressure is minimal, air permeability is maximal and condensation is lowest. In other words, air filtered inside and passing the filter can 20 will most likely flow only through the channels 22 formed in the upper layer of filtering particles 211 where the pressure is minimal, air permeability is maximal and condensation is lowest. Except the upper layer of filtering particles 211 in the filter can 20, it is obvious that most part of the lower layers of filtering particles 212,213 could not perform their air-filtering functions. The final result is, the effective filtering cubic capacity of the filter can 20 is minimized, and the service life of the respirator 2 is shortened.